U.S. patent number 4,657,026 [Application Number 06/885,176] was granted by the patent office on 1987-04-14 for apnea alarm systems.
Invention is credited to James R. Tagg.
United States Patent |
4,657,026 |
Tagg |
April 14, 1987 |
Apnea alarm systems
Abstract
An apnea alarm apparatus detects the cessation of breathing of a
human by monitoring movement of the ribcage by sensor means. The
sensor means are connected to a summing amplifier which provides an
electrical signal indicative of the breathing movement of the
ribcage and upon a change in successive electrical signals, which
indicates apnea, an alarm is activated.
Inventors: |
Tagg; James R. (Pittsburgh,
PA) |
Family
ID: |
25386325 |
Appl.
No.: |
06/885,176 |
Filed: |
July 14, 1986 |
Current U.S.
Class: |
600/534;
600/595 |
Current CPC
Class: |
A61B
5/1102 (20130101); A61B 5/113 (20130101); A61B
5/4818 (20130101); A61B 2562/046 (20130101); A61B
2503/04 (20130101); A61B 2560/0257 (20130101); A61B
5/6891 (20130101) |
Current International
Class: |
A61B
5/11 (20060101); A61B 5/113 (20060101); A61B
005/08 () |
Field of
Search: |
;128/714,721,774,782,722,723,663 ;33/1PT,DIG.13 ;340/665,666 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Howell; Kyle L.
Assistant Examiner: Hinderburg; Max F.
Attorney, Agent or Firm: Buell, Ziesenheim, Beck &
Alstadt
Claims
I claim:
1. An apparatus for detecting the cessation of force from the
acceleration of the mass of the uppermost side of the ribcage from
breathing of a human in a crib or bed having a frame for support
comprising sensor means on said frame which signals a change in
vertical force on said frame as an electrical output signal,
amplifier means receiving the electrical output signals from all
sensor means and providing an output signal, variable gain means in
the amplifier providing matching of the signal with the physical
parameters of the patient, microprocessor means comparing
successive said signals and providing an output signal if a change
occurs and at least one of audible and physical output alarm means
receiving the signal from the microprocessor to signal a change in
state on the sensor means.
2. An apparatus for detecting the cessation of breathing as claimed
in claim 1 wherein each sensor means is a piezo electric transducer
coupled with a fixed gain integrating amplifier.
3. An apparatus for detecting the cessation of breathing as claimed
in claim 1 wherein each sensor means is a strain gauge transducer
coupled with a fixed gain amplifier utilizing integration to zero
the amplifier.
4. An apparatus for detecting the cessation of breathing as claimed
in one of claims 1 or 2 or 3 wherein each sensor means includes a
power source, an amplifier section and an integrator section
delivering a final signal to the summary amplifier from each
leg.
5. An apparatus for detecting the cessation of breathing as claimed
in one of claims 1 or 2 or 3 wherein said sensor means also detects
a change of force in a horizontal plane to allow detection of the
human.
Description
This invention relates to apnea alarm systems and particularly to a
system for continuously monitoring certain critical body functions
of an infant and sounding an alarm if one or more of those
functions ceases or becomes abnormal.
Death from apnea, frequently called "crib death" or "cot death", is
an all too frequent occurrence, particularly in premature infants.
Such deaths occur from the cessation of breathing by the infant.
Death is not immediate upon cessation of breathing and the child
can be revived and breathing induced by proper stimuli and other
means if given in time. This, of course, requires prompt detection
and swift action thereafter. The general nature of the problem has
long been recognized and many attempts at a solution have been
proposed over the years.
Lewis U.S. Pat. No. 3,631,438, provides a mattress, a sensory alarm
and a switch for operating the alarm in the absence of compression
of the mattress after a preset time period from a previously
detected compression. The system requires a compartmentalized air
mattress with air connecting means between the compartments to a
central duct or chamber having an anemometer in the center,
including a thermistor and leads to an alarm system. This is a very
complex system requiring a special mattress and central air
system.
Sielaff U.S. Pat. No. 3,727,606 provides another form of apnea
detector involving again a fluid tight mattress with a connection
to a fluid pressure sensitive transducer which in turn signals a
read out signal device. A pop-off valve is provided for bypassing
large air changes caused by gross body movements. Here again, a
special mattress is required. If for any reason the mattress
develops even a pin hole leak it will become inoperative.
Lawson U.S. Pat. No. 4,146,885, like Lewis provides an apnea
detector involving an anemometer and detection system connected to
a closed cell beneath the infant supported on a resilient
diaphragm. Here again, a special bed and air cell structure is
involved which is expensive and limited in use.
Strube U.S. Pat. No. 4,169,462 discloses an apnea detector designed
to be attached directly to the child to detect body movements. This
form of device is complex and uncomfortable to a child and likely
to be disconnected and produce false alarms by the child's normal
movements.
Other more recent attempts to solve this problem appear in Frost
U.S. Pat. No. 4,245,651 and Friesen et al. U.S. Pat. No. 4,438,771
both of which relate to pad devices which are designed to warn of
cessation of breathing.
All of these devices are basically usable only in a hospital type
environment where their expense can be justified by continual use
and where personnnel are available for maintenance and constant
supervision. Such devices are not of the type or construction
suitable for use in the home where most apnea deaths occur and
where the transient motion of people moving about, of weather and
wind changes, opening and closing of doors and windows, heating and
air condition equipment can play havoc with such prior art
devices.
I have invented an apnea detector which provides a high rejection
of noise caused by the normal atmospheric changes in air pressure
which affect detectors of the air pressure type. My detector
eliminates the danger of strangulation, tape rash, discomfort,
electrocution, false alarms, etc. which occur with devices attached
to the child.
I provide an apparatus for detecting the cessation of breathing of
a human in a crib or bed having a frame for support. The apparatus
includes a sensor means on the frame of the crib or bed which
converts each change in vertical force on said frame to an
electrical output signal. A summing amplifier receiving the
electrical output signals from all sensors on the frame provides an
output summed signal. A variable gain means in the summing
amplifier provides matching of the summed signal with the physical
parameters of the patient, microprocessor means comparing
successive said signals and providing an output signal if a change
occurs and at least one of audible and physical output alarm means
receiving the signal from the microprocessor. Preferably the sensor
means is a piezo electric or strain gauge transducer coupled to an
amplifier to produce an electrical output signal. The alarm means
is preferably a buzzer combined with a flashing light as the
physical output alarm. Preferably, the crib or bed is provided with
a standard foam mat upon which the human rests.
In operation the sensing of the breathing through the foam mat is
possible because when, for example, an infant lies on the mat and
breathes, the uppermost side of the infant's ribcage moves up and
down as the infant inhales and exhales. Since the upper portion of
the ribcage has mass, the moving of this mass in an up and down
motion is an acceleration of a mass, and a force equal and opposite
is exerted against the mat by the infant's body, in particular that
side of the rib cage in contact with the foam mat. The mat in turn
transmits the instantaneous sum of the infant's body weight and the
force from the acceleration of the ribcage mass during breathing to
the frame of the crib or bed and finally to the sensors.
Due to the wide range of signal strength from the sensors resulting
from a wide range of possible patient weights and wide range of
breathing rates, it is necessary for the gain of the amplifier
after the summing of the signals to be variable so that the signal
can be amplified more when low, such as when monitoring a light
weight patient or one with a slow breathing rate. On the other
hand, the signal can be amplified less when monitoring a relatively
heavy patient or one with a fast breathing rate. This matching of
the gain of amplification of the signal to the patient will provide
a usable signal for decoding and analyzing the breathing rate of
the patient throughout the range of patient weight and breathing
rate.
The units can be chained together when used in a nursery to connect
to one alarm at a main nurse's desk along with an alarm light and
audible alarm at each bed unit acting independently to signal the
unit that triggers the alarm.
In the foregoing general description I have set out certain
purposes and advantages of my invention. Other objects, purposes
and advantages of the invention will be apparent from a
consideration of the following description and the accompanying
drawings in which:
FIG. 1 is a schematic isometric view of a bed with transducers
beneath each leg;
FIG. 2 is a schematic isometric view of a bed with a transducer
beneath one leg;
FIGS. 3A, 3B and 3C are schematic side elevation, front elevation
and top plan views of a bed with transducer(s) built into the frame
of the bed at the hanging support;
FIG. 4 is a schematic wiring diagram of a present preferred
embodiment of a low noise amplifier to be used with each strain
gauge sensor; and
FIG. 5 is a block diagram of the entire device showing the
sensor(s), input and variable gain amplifiers, microcomputer,
alarms and power supply.
Referring to the drawings, in FIG. 1, I have illustrated a bed 10
having legs 11 with sensors 12 attached to the frame beneath each
leg. Each sensor 12 is made up of a transducer (which may be a
strain gauge type or a piezo electric type transducer) and a low
noise fixed gain amplifier.
In FIG. 2, I have illustrated bed 10 having legs 11 with a sensor
12 attached to the frame beneath only one of said legs. In such
cases it is desirable to adjust the length of the other three legs
to maintain the crib in a level state. This can be accomplished in
many well known ways, such as by using leveling screws in the legs,
etc.
In FIG. 3, I have illustrated a bed 20 having a main crib section
21 that hangs from supports 22. This configuration uses sensor(s)
23 in the support frame. Sensors 23 are of the same type of sensors
12 described above.
A low noise fixed gain amplifier which might be used with strain
gauge sensor 12 is illustrated in FIG. 4. Such an amplifier
preferably has a power section which supplies power to all sections
of the amplifier 14a, a high stability voltage reference which
supplies a voltage reference to the amplifier bridge section 14b,
an amplifier section 14 containing the strain gauges and an
integrator section 14d which zeros out the constant weight.
Referring to FIG. 5, the low noise amplifier 14 is connected to a
summing amplifier 15 which is in turn connected to a variable gain
amplifier 16. The output of the variable gain amplifier goes to the
signal level comparator 17. The output of the signal level
comparator goes to the microprocessor unit 18. The microprocessor
adjusts the variable gain amplifier so a usable signal is sent to
the signal level comparator. The microprocessor unit 18 is in turn
connected to and energizes one or more alarms 19.
I have found that the sensing of a change in force in the XY
horizontal plane at the sensor allows detection of the patient's
movements.
In the foregoing specification I have set out certain preferred
practices and embodiments of my invention, however it will be
understood that it may be otherwise embodied within the scope of
the following claims.
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